US Scientists Develop New Vaccine Against Ebola Virus - 2003-08-06

U.S. government scientists have developed a speedy vaccine against the deadly Ebola virus, which continues to emerge in central Africa. It protected test monkeys six times faster than an earlier version. The researchers hope it might someday be useful against a quickly spreading infection.

The gruesome Ebola virus kills 50 to 90 percent of its victims. It begins with high fever, severe pain, and malaise followed by bleeding from the eyes, nose, and ears as vessels and organs deteriorate. Death can occur in as little as one week.

Because Ebola acts so rapidly, researcher Gary Nabel of the U.S. government's National Institutes of Health has sought a rapid preventive measure. In the journal Nature, he and his colleagues describe a new vaccine that takes effect very quickly in animals.

"The goal of this study is to try to accelerate the take of the vaccine because in Ebola virus infection, time is a very important element," he said. "Outbreaks occur rapidly, and the sooner you can vaccinate, the sooner the vaccine can begin to protect against infection."

Mr. Nabel's study shows the new vaccine provided fast protection from Ebola infection for eight laboratory monkeys. Just one month after a single inoculation, they were injected with varying amounts of Ebola virus and none died. In contrast, an older version developed in the late 1990s requires four shots over six months.

The older version first introduces non-infectious genetic material from the virus to induce a first level of immunity. Then come three booster injections. But Mr. Nabel's team was able to hasten the process by using just one booster shot, even though it did not provide as much immunity as the longer process does.

"The question we asked in the study was even though the immune response is not as potent, if it comes up more rapidly, can it still protect against the disease? In this case, we found that it is very effective at doing that," he said.

The researchers say if the quick-acting Ebola vaccine works in humans, it might be just the tool to use during outbreaks. But they point out that it would not make the old, four-shot version obsolete. Mr. Nabel says each would be used in different settings.

"There are circumstances where you might find the risk of infection is remote, in which case you might have more time to vaccinate and to generate an immune response that is more long-lasting and more potent," he said. "In the case of this particular study, because we want the immune response to occur quickly, we would actually be thinking about using the vaccine as an intervention. It's a more aggressive approach to vaccination."

The National Institutes of Health is testing the same quick-vaccine strategy with other infectious organisms that cause acute outbreaks and require a rapid response. Among them are the SARS coronavirus and the Marburg and Lassa fever viruses. Researchers hope to have the Ebola vaccine ready for human testing by the end of next year.